Cards | 10 |

Focus | Forces and Energy |

Topics | Force, Kinetic Energy, Magnetism, Mass vs. Weight, Power, Weight, Work |

Force is applied to change an object's **speed** or **direction of motion**.

Kinetic energy is the energy posessed by a moving object. **Potential energy** is stored energy in a stationary object based on its location, position, shape, or state.

Simple magnets have two poles, north and south, and opposite poles attract each other (N attracts S, S attracts N). Likewise, the same pole of two magnets repel (N repels N, S repels S). The Earth has a magnetic field and North and South Poles which enables the use of a **magnetic compass** to determine direction.

Mass is the amount of matter something has while weight is the force exerted on an object's mass by gravity. So, although a person's mass doesn't change when going from the Earth to the Moon, their weight will decrease because the force of the Moon's gravity is much less than that of Earth.

Power is the rate at which work is performed or work per unit time: \(P = {w \over t}\) and is measured in **watts (W)**.

Weight is a force that describes the attraction of **gravity** on an object. Force is measured in **newtons (N)** with 1 N being the force required to impart an acceleration of 1 m/s^{2} to a mass of 1 kg.

Work is performed on an object when an applied force causes displacement along the same vector. Measured in **joules (J) **or **newton-meters (Nm)**, work is calculated by multiplying force times displacement: \(W = \vec{F}\vec{d}\)